Class F motor lead wires are manufactured to conform to UL specifications subject 758, such as Style 3289, which specifies a 600-volt rating and 150.degree. C. temperature rating. The cables are approved by UL for use as motor leads or internal wiring of appliances.
Present UL standard class F motor lead wires, having Average Wire Gauges (AWGs) 9 through 30, have an insulation wall thickness of 0.030 inches. Larger-sized wires require greater wall thicknesses, as shown below:
______________________________________ MINIMUM AVERAGE CONDUCTOR SIZE INSULATION THICKNESS (AWG) (MILS) ______________________________________ 30-9 30 8 45 7-2 60 1-0000 80 ______________________________________
The insulation used on these lead wires is generally a cross-linked polyolefin. The insulations are usually connected to the stator of the motor; they are subjected to a varnish bake process, which comprises a polyester or epoxy base. The insulations are usually coated with a releasing agent, such as Vydax (fluorotelomer dispersion), to protect them from the varnish. They can also be protected by either a fluorocarbon or silicone rubber sleeve.
One problem associated with the above wire construction is the failure to adequately protect the insulation from the varnish. Due to inadequate coating or sleeving, there is a resultant sticking of the varnish to the lead wire, which then often causes the lead wire to crack upon bending.
Another fabrication problem observed with the above-mentioned process is the possible migration of the antioxidant to the insulation surface. Migrating antioxidant prevents the hardening of the varnish during the bake cycle; hence, the uncured varnish will thereafter remain tacky.
The present invention has modified the above wire fabrication process to eliminate the two cited problems. The instant invention also provides a construction having a thinner and less costly insulation.